Automatic vise jaw

ABSTRACT

An automatic vise jaw wherein the movable jaw is urged toward a fixed vise jaw by means of a crank operated screw. The movable jaw includes a housing which terminates forwardly at the movable jaw pressure plate and a cylinder block which is in slideable contact with the housing. The crank operated screw affixes to the cylinder block to maintain the block in a stationary preset position during operation of the device. A pair of air cylinders are provided in the cylinder block which function pistons forwardly and rearwardly in response to applied air pressure. Interconnecting linkage pivotally connects between the cylinder block and the main housing and functions to slide the main housing relative to the cylinder block upon application of air pressure to the cylinders. By employing suitable leverage, the linkage serves to substantially increase the pressure available at the movable jaw over that applied at the air cylinders and to rapidly apply the increased pressure at the pressure plate for work holding purposes.

United States Patent [1 1 Newswanger AUTOMATIC VISE JAW [76] Inventor: Paul S. Newswanger, 1401 Vermont Ave., Lancaster, Pa. 17603 [22] Filed: Apr. 7, 1972 [21] Appl. No.: 242,181

[52] U.S. Cl 269/32, 269/221, 269/228, 269/256 [51] Int. Cl B23q 3/08 [58] Field of Search 269/24, 25, 27, 28, 30, 31, 269/32-34, 221, 228, 256

2,896,515 7/1959 Alexander 269/32 FOREIGN PATENTS OR APPLICATIONS 246,520 4/1966 Austria. 269/34 Primary Examiner-Harold D. Whitehead Assistant Examiner-Harold P. Smith, Jr. Attorney, Agent, or Firm-Karl L. Spivak [4 1 Feb. 19,1974

[57] ABSTRACT An automatic vise jaw wherein the movable jaw is urged toward a fixed vise jaw by means of a crank operated screw. The movable jaw includes a housing which terminates forwardly at the movable jaw pressure plate and a cylinder block which is in slideable contact with the housing. The crank operated screw affixes to the cylinder block to maintain the block in a stationary preset position during operation of the device. A pair of airrcylinders are provided in the cylinder block which function pistons forwardly and rearwardly in response to applied air pressure. Interconnecting linkage pivotally connects between the cylinder block and the main housing and functions to slide the main housing relative to the cylinder block upon application of air pressure to the cylinders. By employing suitable leverage, the linkage serves to substantially increase the pressure available at the movable jaw over that applied at the air cylinders and to rapidly apply the increased pressure at the pressureplate for work holding purposes.

6 Claims, 8 Drawing Figures 'PATENTED 3.792.851

SHEET 1 0F 3 FIG. 2

PAIE FEB 1 s 1914 SHEH 3 BF 3 BACKGROUND OF THE INVENTION The present invention relates generally to the field of machine tools, and more particularly, is directed to an automatic vise jaw for use in holding various work pieces for machine operation.

It is the common practice to employ work holding vises in conjunction with conventional machine tools such as drill presses, milling machines, grinders and similar metal working machinery. Most conventional vises include a stationary jaw and a movable jaw. The movable jaw is generally rendered movable with respect to the fixed jaw by means of a large screw which is rotated by an operating crank. By placing a work piece between the fixed and movable jaws and then turning the crank, a workpiece couldbe tightly gripped between the jaws for machining purposes.

The prior art vises of which I am familiar are relatively slow in operation because the machine operator must manually turn the crank until sufficient pressures are built up to securely hold a workpiece between the fixed and movable jaws of the vise. In those instances wherein it is desired to machine a great number of pieces such as in a production run, the length of time required to alternately tighten and loosen the various work pieces in a vise by means of the hand operated crank is quite time consuming and in the case of some production runs, actually requires more timethan the machining operation itself. Additionally, the pressures generated by the manual efforts of the machinist to tighten the work piece within the vise jaws was directly proportional to the pressures exerted by the machine operator on the crank handle. In order to tighten and loosen a number of pieces during a production run, considerable manual effort on the part of the operator was required. Accordingly, fatigue of the operator was and is an important consideration when planning a production operation. The exertion required to alternately tighten and loosen the movable vise jaw manually by tightening and loosening the crank handle required considerable effort on the part of the operator and usually resulted in noticeable slow down on the part of the operator by the end of a busy day.

Prior workers in the art have attempted to employ the advantages of hydraulic pressure in conjunction with vises to both speed up the work and to increase the available pressure for work holding purposes. For example, hydraulically operated devices have been disclosed in US. Pat. Nos. 2,803,157, 2,050,976 and 2,656,820. All of the prior art automatic vise jaws above referred to incorporate hydraulic pressure means to operate a movable jaw but are notequipped with linkage means to rapidly exert greatly multiplied forces upon a pressure plate to thereby allow rapid interchangeability of work pieces during production runs. Additionally, the prior art devices of which I am familiar are relatively complicated in nature and in construction and are not compatible for use with existing equipment.

In my co-pending application, Ser. No. 158,550, filed June 25, 1971, entitled Automatic Vise Jaw, I have disclosed a linkage operated movable jaw wherein the pressure plate is moved towards the fixed jaw by means of a novel arrangement of air operated pistons and linkage arms. The present device is an improvement over my said prior invention.

SUMMARY OF THE INVENTION The present invention relates to the field of automatic vise jaws, and more particularly, is'directed to an air cylinder operated movable jaw capable of rapidly applying and releasing greatly multiplied hydraulic pressure for work holding purposes.

The present invention is compatible for use with most vises which arepresently in place on various machine tools, such as, milling machines and drill'presses as manufactured by Bridgeport Machine Tool Company. The existing fixed jaw construction and the usual main vise crank operated screw are employed in well known manner and are re-used in conjunction with the present invention. The existing movable jaw is first removed from the vise and is replaced by a movable jaw which is fabricated in accordance with the present invention as hereinafter more fully set forth, a cylinder block is employed which has been machined to accommodate a pair of juxtaposed air cylinders for pressure plate ac tuation by air pressure. A piston is associated with each air cylinder which is arranged for double action wherein the pistons are reciprocated forwardly to function linkage for work holding purposes and rearwar'dly for purposes of rapidly releasing the work. The pistons and associated piston rods function linkage which is suitably pivoted within the movable jaw construction between the cylinder block and the movable housing to exert a greatly increased ratio of pressure upon a work contacting pressure plate. The pressure plate forms the forward face of the movable housing and in conjunction with the existing vise fixed jaw, provides the work holding and work contacting components.

Activation of the air cylinders'to pressurize the rearward face of the piston forces the pistons and the affixed piston rods forwardly to pivot the operating linkage about the various pivot points. The linkage in turn urges the main. housing forwardly with respect to the cylinder block to push the pressure plate toward the fixed jaw for work holding purposes. By judiciously constructing the linkage to increase the pressure ratio, great pressures canbe quickly and easily built up at the pressure plate to securely hold a work piece during the machining operation. When it is desired to release the work piece, air pressure applied at the forward face of the pistons serves to rapidly pull the main housing and the affixed pressure plate from contact with the work piece.

In operation, the machine operator turns the main vise screw by means of the crank to propel the movable jaw until the work piece is loosely held. Optimumly, the part to be machined is freely held between the fixed jaw of the vise and the pressure plate of the movable jaw with a clearance of approximately one sixty-fourth of an inch therebetween. Energization of the air cylinders causes the pistons to activate the linkage which in turn pivots to forwardly press the main housing and the affixed pressure plate a sufficient distance to securely hold the work piece between the fixed jaw and the pressure plate. An entire length of travel of only approximately 0ne-sixteenth of an inch has been found suitable for this purpose. This short length of travel results in faster, more accurate operation and leaves no space in which to trap the fingers of 1 the machine operator betwen the movable jaw and the work piece. Enormous pressures are applied quickly and easily to the work piece by means of the leverage obtained at the operating linkage. After the machining operation is completed, the air switch handle is rotated to apply air pressure to the forward face of the pistons to rapidly retract thepressure plate a distance of approximately onesixteenth of an inch to thereby allow the work piece to be immediately removed from between the pressure plate and the fixed jaw without requiring any further manual adjustment of the vise screw and crank.

It should be noted that once the pressure plate of the movable jaw is properly located with relation to the fixed jaw of the vise by means of the screw and operating crank for a production run of similar parts, the screw and crank need not again be turned or adjusted and all of the work holding operations can be automatically performed by the activation and deactivation of cordingly, when the size of the work changes, the screw can simply be rotated until the movable jaw is brought into the correct new position for work holding purposes without the need for loosening or tightening any clamps or similar devices.

It is therefore an object of the present invention to provide an improved automatic vise jaw of the: type set forth.

It is another object of the present invention to provide a novel automatic vise jaw that is compatible for operation with existing vises and which is designed for use with the existing fixed jaw, base and main adjusting screw.

It, is another object of the present invention to provide a novel automatic vise jaw that includes a cylinder block which affixes to the main screw and a main housing which is moved relative to the cylinder block upon the application of air pressure to the cylinder block.

It is another object of the present invention to provide a novel automatic vise jaw wherein air cylinders are incorporated in conjunction with suitable linkage to increase the ratio of pressure available for work clamping purposes.

It is another object of the present invention to provide a novel automatic'vise jaw which incorporates a stationary cylinder block, a housing which is moved relative to the cylinder block by interconnecting linkage and a pressure plate being moved in vertical planes to squarely apply pressure to a work piece.

It is another object of the present invention to provide a novel automatic vise jaw having a cylinder block, a main housing slidable relative to the cylinder block and interconnecting operating linkage to energize a work holding pressure plate, the said linkage having a generally X-shaped configuration.

' It is another object of the present invention to provide a novel automatic vise jaw having a maximum travel stroke of approximately one-sixteenth of an inch to thereby eliminate the possibility of injury to the fingers of the machine operator. 1 It is another object of the present invention to provide a novel automatic vise jaw which includes a screw connected cylinder-blockya main housing, which is slidable relative to the cylinder block and which includes a forwardly positioned pressure plate, the pressure plate having a relative movement toward and away from the work piece in a planar path of travel.

It is another object of the present invention to provide a novel automatic visejaw that is inexpensive in' in construction, and trouble free taken in conjunction with the accompanying drawings wherein like reference characters refer to similar parts throughout the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a vise assembly incor porating the present invention. I

FIG. 2 is a bottom plan view taken along line 22 of FIG. 1, looking in the direction of the arrows and showing the pressure in the retracted position.

FIG. 3 is a cross sectional view taken along line 33 of FIG. 2, looking in the direction of the arrows and partially broken away to expose interior construction details.

FIG. 4 is a cross sectional view taken along line 44 of FIG. 3, looking in the direction of the arrows and showing the pressure in its pressure applying position and partially broken away to expose interior construction details.

FIG. 5 is a cross sectional view taken along line 55 of FIG. 4, looking in the direction of the arrows.

FIG. 6 is a cross sectional view taken along line 66 of FIG. 5, looking in the direction of the arrows.

FIG. 7 is a cross sectional view taken along line 77 of FIG. 6, looking in the direction of the arrows and showing the hollow air shaft in position to advance the movable jaw.

FIG. 8 is a cross sectional view similar to FIG. 7, showing the hollow air shaft in position to retract the movable jaw.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of my invention selected for illustration in the drawings and are not intended to define or limit the scope of the invention.

Referring now to the drawings, I shown in FIG. 1, a machine vise 10 which includes a stationary base 12 which is adaptable to be mounted upon the table 14 of a conventional machine tool such as a milling machine or a drill press 16. The stationary base 12 conventionally mounts upon the table 14 by utilizing mounting bolts 18 for other suitable fastening means in well known manner. The stationary base 12 forwardly supports the fixed vise jaw 20 and terminates rearwardly in a conventional vertical support 22 in the usual manner. The vertical support 22 is provided with an internally threaded opening which threadedly receives main vise screw 24 in conventional threaded engagement therein. The main vise screw 24 terminates rearwardly in a rectangular end 26 to re'movably receive a crank handle (not shown) in conventional manner. The main vise screw 24 forwardly engages the movable vise jaw 28 and serves to move themovable vise jaw 28 relative to the stationary base 12 to secure a work piece in the vise 10. Thus, by rotating the main vise screw 24 within the threaded socket in the vertical support 22, the movable jaw 28 may be moved forwardly or rearwardly in conventional manner relative to the stationary base 12 to thereby vary the spacing between the pressure plate 30 of the movable vise jaw 28 and the fixed plate 32 of the fixed vise jaw 20.

As best seen in FIGS. 2, 3, 4, and 5, the movable vise jaw includes a cylinder block 34 which is in sliding engagement within the main housing 36. An opening 38 is provided in the rear wall 40 of the main housing 36 through which the forward end of the main vise screw 24 is positioned; The cylinder block 34 is drilled and machined to provide a threaded socket 42 which receives the forward end of the main vise screw 24 therein. It will be noted that there is no connection between the main housing 36 and the main vise screw 24 so that function of the air cylinders 44, 46 will result-in movement of the main housing 36 relative to the cylinder block 34 which will be retained in stationary relationship by means of the main vise screw 24 as hereinafter more fully set forth.

The cylinder block 34 is drilled or otherwise treated to provide a pair of spaced, longitudinally extending air cylinders 44, 46. A pair of similar pistons 48, 50 respectively reciprocate within the air cylinders 44, 46 when air pressure is applied and longitudinally reciprocate their respective associated piston rods 52, 54.

An air intake assembly 56 mounts upon the side of the main housing 36 and is provided with an air inlet connection 58 which is of conventional design to receive an air hose 60 in an air tight junction. The air intake assembly 56 includes an operating handle 62 which is connected in conventional manner to turn a partially hollow shaft 64 which is rotatably mounted within the air intake assembly block 66. See 'FIGS. 6, 7 and 8. The shaft 64 is machined to provide a cylindrical, hollow interior passage 68 which is subdivided into two equal portions by a medially positioned block 70 to effectively subdivide the air passage 68 into right and left air compartments 72, 74. The air intake assembly block 66 is affixed to the cylinder block 34 by means ofa pair of threaded, hollow bolts 76, 78, each of which is respectively provided with an interior air channel 80, 82 to permit passage of air from the hollow shaft air passage 68 to the cylinders 44, 46 in a manner hereinafter more fully set forth.

As best seen in FIGS. 5-8, the air intake assembly block 66 is provided with a pair of short air passages 84, 86 which respectively communicate between a bolt air channel 80, 82 and therespective right and left compartments 72, 74 of the hollow air passage 68. Thus air from the right air compartment 72 can be introduced into and received from the hollow bolt air channel 82 and air from the left compartment 74 can be introduced into and received from the hollow bolt air channel through the respective short air passages 84, 86. The air intake assembly block 66 is additionally drilled to provide communicating passages '88, to respectively connect the right and left compartments 72, 74 with the air inlet connection 58. The hollow shaft 64 is provided with right openings 92, 94 which register with the short air passage 86 and the communicating passageway 88 when the handle 62 is turned to a first position. See FIG. 7. Similarly, the hollow shaft 64 is drilled to provide a pair of left openings 96, 98 which communicate with the short air passage 84 and the communicating passageway 90 when the handle 62 is turned to its second position. See FIG. 8. Additionally, the left compartment 74 is drilled to providea bleed opening 100 which communicates with a short air passage 84 when the handle 62 is turned to its first position as in FIG. 7. The right compartment 72 is similarly provided with a bleed opening 102 which communicates with'the short air passage 86 when the handle 62 is turned to'its second position as in FIG. 8.

Referring now to FIGS. 2, 4 and 5, it will be seen that a rearward transverse air duct 104 is drilled through the cylinder block 34 and the main housing 36 and communicates with the hollow bolt air channel 82. The air duct 104 communicates with the respective pressure sides 108, of the cylinders 44, 46 through the respective cylinder block opening 112, 114. Accordingly, when the operating handle'62 is turned to its first position as in FIG. 7, air from the air hose 60 is introduced through the air inlet connection 58 through the communicating passageway 88 into the right compartment 72 of the hollow air passage 68. The pressurized air is introduced into the short air passageway 86 through the right opening 92 to pressurize the air duct 104 through the hollow bolt air passage 82. The introduction of air pressure into the pressure sides 108, 110 of the cylinders 44, 46 acts against the pistons 48, 50 to urge the main housing 36 forwardly with respect to the cylinder block 34 as in FIG. 4, by means of the operating linkage system 116 as hereinafter more fully set forth.

Similarly, by turning the handle 62 to its second position as in FIG. 8, air from the air inlet connection 58 is fed into the left compartment 74 through the communicating passageway 90 and the left opening 96. The pressurized air exits the left compartment 74 through the left opening 98 and enters the hollow bolt air channel 80 through the short air passage 84. The air from the left compartment 74 is then introduced into the forward transverse air duct 106 to thereby pressurize the relief sides 118, 120 of the cylinders 44, 46. The air pushes the pistons 48, 50 rearwardly within the cylinders to pull the operating linkage system 116 rearwardly. Movement of the linkage system to its rearward position urges. the pressure plate 30 away from the fixed vise plate 32 in the manner hereinafter more fully set forth. j 1 As best seen in FIGS. 2, 3 and 4, the piston rod 52 terminates forwardly in a generally U shaped connector 126 and is directly connected thereto by means of the pin 128. Similarly, the piston rod 54 terminates forwardly in a second U shaped connector 130 and is directly connected thereto by means of the pin 132. Accordingly, when the piston rods 52, 54 are urged forwardly and rearwardly by air pressure introduced through movementof the handle 62, the U shaped connectors 126, 130 similarly move forwardly and rearwardly toward and away from the fixed jaw 32 of the vise.

The operating linkage system 1 l6 comprisesa pair of 7 reciprocate their respective affixed piston rods 52, 54, the respective connections between the grooves 144, 148 and the cam curved surfaces 142, 146 of the levers 134, 136 pull the ends of the levers in the direction of action of the pistons. The second end 150 of the L- shaped levers 134 is widened to accommodate a pair of spaced pivots 152, 154 to provide a crank action. It will be noted that the length of the levers 134 is many times greater than the distance between the pivots 152, 154 to thereby generate great leverage forces. The pivot 152 interconnects between the main housing 36 and the Lshaped levers 134. The pivot 154 connects the rear section of the second lever end 150 with the operating links 156 in a pivotal connection. The other end of the operating links 156 are pivotally connected with the main cylinder block, 34 in a pinned, pivotal connection 158. I

Similarly, the second end 160 of the L-shaped levers 136 are pivotally connected to the main housing 36 at the pivot 162 and rearwardly connect to the operating links 164 by means of the pivotal connection 166. The other end of the operating links 164 pivotally connects to the cylinder block 34 in a pivotal connection 168. It will be noted that all of the levers comprising the operating linkage system 116 are generally L-shaped in configuration and are pivoted about the foot of the L. The

levers 134, 136 are also pivoted at the foot of the L at the pivotal connections 154, 166 with the operating links 156, 164 in a manner to move the main housing 36 relative to the cylinder block 34 when the pistons ,48, 50 are activated. When the pressure sides 108, 110

of the cylinders-44, 46 are pressurized, the pistons 48, 50 push the levers 134, 136 about their respective pivots 152, 162 until the pivotal connections 152, 154,

1 458 and 162, 16,6 and 168 are respectively in line. See

FIG. 4.-ln this position,the main housing 36 is pushed forwardly of the cylinder block 34 for work holding purposes. it will be noted in this position that the pressure plate 30 is pushed to its forwardmost limit of travel for work holding purposes.

By pressurizing the relief sides 118, 120 of the cylinders 44, 46, the respective piston rods 52, 54 are pushed rearwardly to thereby urge the L-shaped levers 134, 136 to pivot about the pivotal connections 152, 162 to assume the position illustrated in FIG. 2. In this position, the main housing-36 is pulled rearwardly with respect to the cylinder block 34 so that the pressure plate 30 is pulled to its rearwardmost position to thereby release a work piece (not shown). As hereinbefore stated, all of the L-shaped levers 134, 136 are pinned intermediately by the pin 138 and slot 140 so that there is a complete synchronism of action when both cylinders 44, 46 are pressurized in either direction. The configuration of the operating linkage system 116 builds tremendous pressures for work holding purposes due to the leverage available. It will be noted that when all three pivot points 152, 154, 158'and 162, 166, 168 lie in the same plane, maximum pressure is then applied to the work for work holding purposes. The total length of travel of the movable pressure plate 30 is preferably approximately one-sixteenth of an inch so that there is no possibility of a workman having his fingers crushed by the automatic operation of the device.

In order to facilitate the operation of the device, the left air compartment 74 is provided with a bleed opening 168 which registers with the lead opening 170 which is drilled through the air intake assembly block 66 for relief of air from one side of the cylinder 44, 46 when the other side is pressurized. Similarly, the right compartment 72 of the hollow air passage 68 is provided with a bleed opening 172 which registers with the bleed opening 174 which is drilled through the air intake assembly block 66 when the handle 62 is moved to the position of FIG. 8 for air bleeding purposes.

1 claim:

1. In an automatic vise jaw of the type wherein a movable jaw is manually moved relative to the stationary base by means of a main vise screw, the combination of A. a cylinder block movable over the stationary base,

said cylinder block being moved to a desired position by the said main vise screw,

1. said cylinder block being drilled to provide cylin-' ders and air passages to the cylinders; B. a main housing associated with the cylinder block and being slidable with respect thereto,

1. said main housing being movable from a rearward position to a forward, work holding position upon pressurization of the said cylinders,

2. said main housing being movable with respect to the said main vise screw;

C. operating linkage interconnected between the main housing and the said cylinder block,

1. said operating linkage having a first position wherein the main housing is pulled rearwardly with respect to the cylinder block,

'2. said linkage having a second position wherein the main housingis pushed forwardly relative to the said cylinder block,

3. said linkage including cam curved surfaces;

D. air input means pressurizing the said cylinders, said air input means functioning the said operating linkage between its said first and second position;

E. pistons operable within the said cylinders,

1. said pistons operating piston rods, said piston rods terminating forwardly in connectors which function the said operating linkage,

2. the said connectors being generally U-shaped in configuration, and

3. the said cam curved surfaces being in sliding contact within the U-shaped connectors.

2. The invention of claim 1 wherein the operating linkage includes levers of general L-shaped configuration, the top of the L forming the said cam curved surfaces. I

3. The invention of claim 2 wherein the L-shaped levers include pivotal connections at the base of the L configuration.

4. The invention of claim 3 wherein one said pivotal connection pivotally connects to the said main housing and the other said pivotal connection is pivotally associated with the said cylinder block.

5. The invention of claim 2 wherein the operating linkage system incorporates pairs of oppositely disposed L-shaped levers, the said levers being medially pinned for synchronisrn of action.

6. The invention of claim 5 wherein .the medially pinned connection includes pins associated with the levers disposed in a first direction, said pins riding within elongated slots which are provided in the said levers which are disposed in the opposite direction. 

1. In an automatic vise jaw of the type wherein a movable jaw is manually moved relative to the stationary base by means of a main vise screw, the combination of A. a cylinder block movable over the stationary base, said cylinder block being moved to a desired position by the said main vise screw,
 1. said cylinder block being drilled to provide cylinders and air passages to the cylinders; B. a main housing associated with the cylinder block and being slidable with respect thereto,
 1. said main housing being movable from a rearward position to a forward, work holding position upon pressurization of the said cylinders,
 2. said main housing being movable with respect to the said main vise screw; C. operating linkage interconnected between the main housing and the said cylinder block,
 1. said operating linkage having a first position wherein the main housing is pulled rearwardly with respect to the cylinder block,
 2. said linkage having a second position wherein the main housing is pushed forwardly relative to the said cylinder block,
 3. said linkage including cam curved surfaces; D. air input means pressurizing the said cylinders, said air input means functioning the said operating linkage between its said first and second position; E. pistons operable within the said cylinders,
 1. said pistons operating piston rods, said piston rods terminating forwardly in connectors which function the said operating linkage,
 2. the said connectors being generally U-shaped in configuration, and
 3. the said cam curved surfaces being in sliding contact within the U-shaped connectors.
 2. said main housing being movable with respect to the said main vise screw; C. operating linkage interconnected between the main housing and the said cylinder block,
 2. said linkage having a second position wherein the main housing is pushed forwardly relative to the said cylinder block,
 2. the said connectors being generally U-shaped in configuration, and
 2. The invention of claim 1 wherein the operating linkage includes levers of general L-shaped configuration, the top of the L forming the said cam curved surfaces.
 3. The invention of claim 2 wherein the L-shaped levers include pivotal connections at the base of the L configuration.
 3. the said cam curved surfaces being in sliding contact within the U-shaped connectors.
 3. said linkage including cam curved surfaces; D. air input means pressurizing the said cylinders, said air input means functioning the said operating linkage between its said first and second position; E. pistons operable within the said cylinders,
 4. The invention of claim 3 whereIn one said pivotal connection pivotally connects to the said main housing and the other said pivotal connection is pivotally associated with the said cylinder block.
 5. The invention of claim 2 wherein the operating linkage system incorporates pairs of oppositely disposed L-shaped levers, the said levers being medially pinned for synchronism of action.
 6. The invention of claim 5 wherein the medially pinned connection includes pins associated with the levers disposed in a first direction, said pins riding within elongated slots which are provided in the said levers which are disposed in the opposite direction. 